[PSUBS-MAILIST] Terminating a conical transition

Sun May 4 17:43:19 EDT 2014

Joe,
Sounds like you need to have the longest cones possible at each end to reduce the size of the free flooded areas.  Another option is to change the design, decide what your priorities are.  What is most important? if long transits are the plan then you may need to change things.  If fuel cost is a consideration, another change.  Looking very cool dock side, you nailed it. It just wouldn't be fun if it was easy.
Hank
--------------------------------------------
On Sun, 5/4/14, Joe Perkel via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

 Subject: Re: [PSUBS-MAILIST] Terminating a conical transition
 To: "Personal Submersibles General Discussion" <personal_submersibles at psubs.org>
 Received: Sunday, May 4, 2014, 5:30 PM

 Sean,
 Have
 you ever notice how the Civil War design of the USS
 Alligator stabilized the boat submerged? A couple of crazy
 little tethered floats, but the rationale has
 never escaped me.
 I
 will reduce free flood space wherever I can. Trapped
 inertia being on my mind, but I needed someone to remind me
 of the waste in efficiency / power requirements,
 thanks! Also, your comments bring home some compelling
 reasons to shorten the design with a "Just
 enough but no more" design
 mindset.
 I've
 given thought to the conical section in the front, I can
 reduce this down to a 30" head with forward viewing ala
 Kraka, but quite the tight fit! Not sure, I have to give it
 some more thought.
 If
 I reduce the aft end with a cone, then I would bring the
 motor inside and do a standard marine hybrid
 installation. Expensive, but certainly a more reliable
 answer. If I do that, I would dispense with the notion of
 propulsion units in the aft end of the pods, truly no
  need then. This boat requires a  massive
 ventilation / climate control scheme for surface operations,
 that's why I've been overly generous with the
 machinery space in these early drafts.
 I'm
 still concerned about stability because I have to contend
 with what to do with all of that centerline space. The VBT
 would take up some, but I would have to flood the
 rest.
 Thanks
 again Sean!
 Joe
     On Sunday, May 4,
 2014 4:56 PM, Joe Perkel via Personal_Submersibles
 <personal_submersibles at psubs.org> wrote:
     Hank,
 What
 you see there is the
  original Seehund arrangement, my intention is as you say,
 up higher. The aft cone on mine essentially now an MBT.
 Those lower volumes will be flooded in practice, but I am
 wondering if they could be blown down dry to help with
 trailer launching and recovery??
 Plenty,
 and I mean plenty of room along the centerline for keel
 ballast.
 I
 keep thinking about what you've told me regarding Gammas
 attachment, always in the back of my
  mind!
 Thanks
 Hank!
 Joe
     On Sunday, May 4,
 2014 4:34 PM, hank pronk via Personal_Submersibles
 <personal_submersibles at psubs.org> wrote:
     Joe,
 Your dive tanks are to low, they should be at
 the top of the sub.  The way you have it will be less
 stable.
 The motor pod should be okay, just
 like the K subs. You do not want your torpedo's to be
 buoyant, they should be as heavy as possible for
 stability.
 Hank
 --------------------------------------------
 On
  Sun, 5/4/14, Joe Perkel via Personal_Submersibles <personal_submersibles at psubs.org>
 wrote:

  Subject: Re:
 [PSUBS-MAILIST] Terminating a conical transition
  To: "Personal Submersibles General
 Discussion" <personal_submersibles at psubs.org>
  Received: Sunday, May 4, 2014, 3:07 PM

  I've incorporated
  some of the suggestions in the attached
 drawing. Still,
  I've got a lot to think
 about here but I am also excited
  about the
 possibilities and the potential outcome. This
  image should give some idea of
  what's on my mind.
  What you see is the
 water ballast arrangement
  on the original
 Seehund, and how my proposed pressure

 boundary fits into this scaled down version. The
 following
  is a list of concerns and or
 design
  considerations.

 1)
  Clearly, I have no need to compensate
 for the loss of

  torpedoes
  2)
  New pressure
 boundary provides for massive MBT volumes

 (Low pressure compressor to blow down

 volumes)
  3)
  Torpedo
 battery pods may need to incorporate some free
  flooding spaces to reduce weight, or perhaps
 reduce battery capacity to a single pod in

 lieu of the former forward water ballast tank, then
  completely free flood both torpedoes
 completely??.
  (Boat will incorporate a
 gen-set)
  4) Questionable

 reliability of external motor pod assembly.

 5)
  Stability considerations
  Thanks for the input
  gents,
 It really helps me to take a step back on

 occasion!
  Joe

       On
 Sunday,
  May 4,
  2014 10:19 AM, hank pronk via
 Personal_Submersibles
  <personal_submersibles at psubs.org>
 wrote:
      Joe,

 When I mounted the tanks back on
  Gamma, I changed the
  mounting location to
 give a greater angle also I did what
  Vance
 is saying on a small scale.    I then poured
  a gallon of paint in 
   each tank and rolled the sub slowly to
 ensure there was
  complete paint
 coverage.  If I was operating in salt

 water I would mount some nipples to the tanks with
  plugs.  After a dive in salt water,
 remove the plug and
  you have access to
 spray fresh water inside and rinse the
  salt
 water out. A large panel is a good idea also because
  you
  can open it up after each
 dive and let it dry out.   
  If I
 had a K350, I would not copy the Nekton tanks
  exactly.  I would change the shape so
 they have more
  volume at the top reducing
 the
  rolling effect. Also I would
  consider
 making them from SS. Also SS heads solves the
  problems entirely. Start watching ebay for ss
 heads.  I
  once saw a ss tank exactly
 the
  same as a 500gal propane tank
  for 1,500
 dollars on ebay.
  Hank

 --------------------------------------------
  On Sun, 5/4/14, via Personal_Submersibles
 <personal_submersibles at psubs.org>
 wrote:

 Subject: Re: [PSUBS-MAILIST] Terminating a conical
  transition
   To: personal_submersibles at psubs.org
   Received: Sunday, May 4, 2014, 8:32
 AM

   Joe,

   Consider using an elliptical head back
 there, for
   starters. You aren't
 building for much depth here, so
   the
 K-350 size will be fine (.375" ish). The ellipses
   are cheaper, do the same job, and give
 you a touch more
   inside
 room. Then I would have
  a cone rolled
   with a short flange on
 the major diameter, maybe a couple
  of
   inches, to match the hull OD.

   The Nekton
 cone-to-dome caused a
   pinch point
 that was always a hassle to clean and paint,
  and
   ultimately left
 some pitting in the pressure hull that had
   to
   be
 weld-repaired. A short cylinder on the sheet metal
   would give you a little more room under
 there to sandblast
   and paint during
 assembly and later for overhauls. I would
   say for maintenance a couple of
 flush-mount, gasketed
  panels
   in the tank would serve you well.
 Don't make them
  too
   ornery to remove or you
 won't do it as often as you
  will
   wish you had.

   I'm wondering now about my own
   boat and using tanks like that. Is there
  anyone in the
  group

 who can plug and chug a metacentric height on Nekton
 tanks
   installed on a K-350? Assembly
 would be so simple that
  way.
   And it would tow better, which is always
 a good thing. The
   Nektons roll a bit,
 but are reasonably stable. A K with
  the
   pods should have plenty of weight down
 low. Hmm. Would it
   work? I'm
 thinking yes. Anybody else have an opinion

 on
   that?

   Vance

   -----Original
   Message-----

   From: Joe Perkel via
 Personal_Submersibles
   <personal_submersibles at psubs.org>

   To:
 personal_submersibles
   <personal_submersibles at psubs.org>

   Sent: Sun, May
 4, 2014 12:28 am

   Subject: Re: [PSUBS-MAILIST] Terminating
 a conical
   transition

   Vance,

   Rethinking that aft assembly to make it
 all soft tanks aft
   of a hemi head ala
 Nekton.

   If I
 go weld-on to the head ala Nekton, how best to attach
   to the head to allow for periodic access
 and maintenance?

   Joe

   Sent from Yahoo Mail for iPad 

  From:

              via
  Personal_Submersibles <personal_submersibles at psubs.org>;

  To:

           <personal_submersibles at psubs.org>;

  Subject:

          Re:
  [PSUBS-MAILIST] Terminating
   a conical transition     

 Sent:

              Sat, May 3,
 2014
  2:03:36 PM     

    Joe,

   It
   seems like an expensive and complex
 assembly for what you
   get. Why not
 close the aft segment in a simpler way and
  fair
   the stern to the
 shape you prefer? A hemisphere with an
   extended shaft housing to put the prop
 where you want it,
   for instance.

   Vance

   -----Original

 Message-----

   From: Joe Perkel via
 Personal_Submersibles <personal_submersibles at psubs.org>

   To: Personal Submersibles General
 Discussion <personal_submersibles at psubs.org>

   Sent: Sat, May 3, 2014 8:17 am

   Subject: Re: [PSUBS-MAILIST] Terminating
 a conical
   transition

   Sean,

   Yes,
   a bolted
 flange with O ring.

   I've
   attached an image of what's on my
 mind. This hull is
   36" OD,
 cylinder length is 120". Anything bigger
   in diameter, simply gets way to big and
 bulky for
   handling.

   I'm
   thinking at this size, I must bolt at
 least two hull
   sections together for
 outfitting and maintenance, and the

 cones can be un-stiffened or perhaps only at the
   joints.

   Joe

     On
 Friday, May
   2, 2014 9:50 PM, Sean T.
 Stevenson via
  Personal_Submersibles
   <personal_submersibles at psubs.org>
   wrote:

   Each cone
 section in that case is considered

 alone, so if you were using stiffeners, you would need a
   heavy stiffener at every joint.
 Depending on the size, it
   may be
 simpler to use unstiffened geometry for such an

  assembly.

   The rules do not address bolting
 pressure
   hull sections together, but
 I don't see why you
   couldn't,
 provided you meet the requirements in terms

 of
   the stress analysis under the
 maximum combined loading
   conditions,
 which are prescribed in the ABS rules.
   Might
   require
 some FEA to be sure. You're thinking an O-ring
   groove seal? Or other arrangement? 
 I think an ASME
   code compliant flange
 would be a good place to start, but
  I
   would make sure that the cross-sectional
 area of each half
   of the flange
 considered individually met the requirements
   of
  a heavy stiffener per ABS, at a minimum material
  location
   (bolt hole). I
 would also be inclined to use SuperBolts

 for
   the connection. 

   http://www.nord-lock.com/superbolt/multi-jackbolt-tensioners/

   Sean

   On May 2, 2014
 6:03:21
   PM MDT, Joe Perkel via
 Personal_Submersibles <personal_submersibles at psubs.org>

   wrote:
   Sean,

   Would the heavy stiffener rule apply
 equally to several
  cone
   segments stepping down at different
 angles?

   Also, do ASME
 pipe flange specifications translate equally
   to bolted
  pressure hull sections? Have I missed a section
   somewhere on bolted cylindrical
 sections?

   Very helpful
 Sean thank you!

   Joe

   Sent from Yahoo Mail for iPad 

  From:

          Sean T. Stevenson
  via

 Personal_Submersibles <personal_submersibles at psubs.org>; 

            To:

            Personal
  Submersibles General

 Discussion <personal_submersibles at psubs.org>; 

 Subject:

              Re:
  [PSUBS-MAILIST] Terminating
   a conical transition     

  Sent:

          Fri, May 2, 2014
  11:45:11 PM    

   2:1
 semi-elliptical heads are usually

 fabricated with some
  length of straight flange (tangential
   cylindrical section) beyond the axis of
 the ellipse.
   Hemispherical heads may
 or may not have a straight flange

 section, but in either case are
  permissible to use
  adjacent
   to conical sections, provided all other
 requirements are
   met. For stiffened
 cones, you must have stiffeners meeting
   the "heavy stiffener" criteria
 at both ends, as
   close as practicable
 to the cone-to-cylinder and

 cone-to-head transitions. For unstiffened cones, the
  length
   L_c used in
 overall buckling calculations must be the

 total
   length between the next heavy
 stiffener to either side of
   the
 entire compartment length, or between the 40% of head
   depth points if otherwise
   unbounded.  Cone to head
   welds are done in the same manner as
 cone to cylinder
  welds,
   and if your

    head is supplied w!
    ith a
   flange, it is the same

   thing.

   Sean

   On May 2, 2014 2:48:52
   PM MDT, Joe Perkel via
 Personal_Submersibles <personal_submersibles at psubs.org>
   wrote:

   I have
   spotted the ABS diagrams and
 specifications for
   re-enforcement and
 butt welds at conical to cylinder

 transitions. I am somewhat unclear however as to
  terminating

  at the head.

   For
   example, the
 diagrams in the 2014 ABS underwater vehicles
   and hyperbaric chamber publication shows
 conical
  transitions

 either bordered by a
   cylinder at
 either end, or simply
  open
   at the small end???

    I want to terminate the small end of a
 conical
  transition

 directly to a small diameter hemi-head without another
   straight section, but I am unclear
 as to whether or
  not

 that is acceptable
    in practice.

   Joe

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